This invention pertains to armatures for electromagnetic launcher systems; and more particularly to conducting phase change material armatures, comprising phase-change materials that melt from solid to liquid at temperatures lower than the melt temperatures of non-phase change material and are conductive in solid and liquid forms thereby absorbing the resistivity generated heat of the armature's slide along the conductive rails of an electromagnetic projectile launcher.
Electromagnetic projectile launchers are known which comprise; a pair of generally parallel conductor rails, a sliding conductive armature placed between the rails, providing a contact between them both and a source of high current. The passage of electrical current through the rails and the armature produces an electromagnetic force on the armature which propels it along the conductive rails. The magnetic field of the current in the rails interacts with the current in the armature to accelerate the projectile. This electromagnetic rail gun launcher has been designed with either a solid armature or a plasma armature.
A plasma armature radiates a significant amount of heat to the rails due to its high temperature, and the plasma may arc erratically, creating local hot spots on the rails. The combination of these two effects produces local melting or ablation of the rail material.
A solid armature can be designed to carry current nearly uniformly throughout its volume. Heat generated at the sliding contact surface of the armature due to friction and contact resistance losses is mild compared to plasma heating. However, heat is also generated throughout the volume of the armature due to resistance losses. To accommodate this resistance heating, solid armatures have been designed to contain enough conductive material so that this heat can be absorbed without an excessive temperature rise. However, for long launch times associated with long rail gun barrels, the mass of the armature can exceed reasonable limits imposed by system requirements on the projectile mass.
The U.S. Pat. No. 4,369,691 to Frederick J. Baehr, Jr., et al. issued Jan. 25, 1983, entitled, "Projectile Launching System with Resistive Insert in the Breech", discloses resistive inserts disposed in the breech of the projectile launcher to prevent excessive premature heating, to prevent premature movement of the projectile armature, and to prevent welding of the armature to the projectile rails during the period while the current builds up to the launching magnitude.
The U.S. Pat. No. 4,430,921 to William F. Hughes, et al. issued Feb. 14, 1984, entitled, "Armature with Graded Laminations", discloses an armature for conducting very large currents between a pair of electrically conductive parallel rails which comprises a plurality of laminations of electrically conductive material spaced in the direction of armature movement from the breech end toward the muzzle end of the rails. Wherein, by grading the conductivity of the laminations, the current density is equalized across all of the laminations.
Finally, the U.S. Pat. No. 4,467,696 to Ian R. McNab et al., issued Aug. 28, 1984, entitled "Electromagnetic Projectile Launcher with Combination Plasma/Conductor Armature" discloses a combination plasma/conductor armature structure which serves to conduct current between a pair of generally parallel conductor rails propelling a projectile along the rails.
It is the primary object of the present invention to provide an electromagnetic launcher system, and more specifically an armature which is operable to dissipate resistive heat during launch without a significant increase in armature mass.